Large-scale and economic purification of therapeutic proteins and especially monoclonal antibodies is an increasingly important problem for the biotechnology industry. Generally, proteins are produced by cell culture, using either mammalian or bacterial cell lines engineered to produce the protein of interest such as a monoclonal antibody. However, once produced, the proteins have to be separated from various impurities such as, host cell proteins (HCPs), endotoxins, viruses, DNA etc.
In a typical purification process, once a protein of interest is expressed in cell culture, the cell culture feed is subjected to a clarification step for removal of cell debris. The clarified cell culture feed containing the protein of interest is then subjected to one or more chromatography steps, which may include an affinity chromatography step or a cation exchange chromatography step. In order to ensure safety of a protein of interest, especially in case of a therapeutic candidate, it is necessary to inactivate any viruses which may be present in a sample containing the protein of interest during the purification process. Generally, virus inactivation is performed after a chromatography step (e.g. after affinity chromatography or after cation exchange chromatography). Typically, in a large scale process, following a chromatography step, an elution pool containing the protein of interest is collected in a large tank or reservoir and subjected to a virus inactivation step/process for an extended period of time with mixing, which may take several hours to a day or longer, in order to achieve complete inactivation of any viruses that may be present in the elution pool.
Several virus inactivation techniques are known in the art including, temperature, pH, radiation and exposure to certain chemical agents.